// C++ code to print BFS traversal from a given
// source vertex

#include <bits/stdc++.h>
using namespace std;

struct EndPoint {
    EndPoint(int v, int w) {
        this->v = v;
        this->w = w;
    }
    int v;
    int w;
};

// This class represents a directed graph using
// adjacency list representation
class Graph {
    // No. of vertices
    int V;
    bool directed;
    vector<list<EndPoint>> pred;
    vector<list<EndPoint>> succ;
 
public:
    // Constructor
    Graph(int V, bool directed);
 
    // Function to add an edge to graph
    void addEdge(int v, int u, int w);

    void addEdge(int v, int u);
 
    // Prints BFS traversal from a given source s
    void BFS(int s);

    // s:源
    // dist:到源s的距离
    // path:每个节点从哪个节点来
    void Dijktrast(int s, vector<int>& dist, vector<int>& path);

    void Naive(int s);

    // 单源最短路
    void SSSP(int s);
};
 
Graph::Graph(int V, bool directed)
{
    this->directed = directed;
    this->V = V;
    adj.resize(V);
}
 
void Graph::addEdge(int v, int u, int w)
{
    // Add w to v’s list.
    adj[v].push_back(make_pair<u, w>);
}

void Graph::addEdge(int v, int u)
{
    addEdge(v, u, 1);
}
 
void Graph::BFS(int s)
{
    // Mark all the vertices as not visited
    vector<bool> visited;
    visited.resize(V, false);
 
    // Create a queue for BFS
    list<int> queue;
 
    // Mark the current node as visited and enqueue it
    visited[s] = true;
    queue.push_back(s);
 
    while (!queue.empty()) {
 
        // Dequeue a vertex from queue and print it
        s = queue.front();
        cout << s << " ";
        queue.pop_front();
 
        // Get all adjacent vertices of the dequeued
        // vertex s.
        // If an adjacent has not been visited,
        // then mark it visited and enqueue it
        for (auto adjacent : adj[s]) {
            if (!visited[adjacent]) {
                visited[adjacent] = true;
                queue.push_back(adjacent);
            }
        }
    }
}

void Graph::Dijktrast(int s, vector<int>& dist, vector<int>& path)
{
}

// Driver code
int main()
{
    // Create a graph given in the above diagram
    Graph g(4);
    g.addEdge(0, 1);
    g.addEdge(0, 2);
    g.addEdge(1, 2);
    g.addEdge(2, 0);
    g.addEdge(2, 3);
    g.addEdge(3, 3);
 
    cout << "Following is Breadth First Traversal "
         << "(starting from vertex 2) \n";
    g.BFS(2);

    iota()
 
    return 0;
}